Since the fetal heart is located within the uterus, the possibility of directly detecting the fetal heart frequency does not exist there, and therefore conventionally required electrocardiodiagram control while the patient holds his breath is not possible during the measurement. Therefore visualizing of anomalies of the heart and large vessels by MRI (magnetic resonance imaging) is not achievable.
For examination of a fetal heart by means of MRT, for example Manganaro et al., Prenat. Diagn. 2008, 28, 148-156, and Fogel et al., Fetal Diagn. Ther. 2005, 20, 475-480, describe True fast imaging with steady-state precision (True FISP) and real-time cine-MR-sequences to be used, whereby in these cases the procedure is carried out without control (triggering). Nijm et al., J. Magn. Reson. Imaging 2008, 28, 767-772 use self-gating (SG) algorithms for synchronization. Here among other things the low signal-to-noise ratio is limiting. Yamamura et al., Eur. Radiol. 2009, 19, 2383-90, use an invasive trigger system (Pulse wave triggering). All these methods have severe limitations, which either render their practical use on a human being impossible, or there is no yield of images of sufficient quality, which allow for evaluating anatomic structures and functional information.
Michel et al., American Journal of Roentgenologie 2003, 180, 1159-1164, come to the conclusion that fetal CTG during magnetic resonance tomography is feasible with modified standard equipment. However, it is also stated that, due to technical reasons, CTG monitoring while the patient is in the magnet is not possible (rather, measurements were made immediately after leaving the magnet). Accordingly, the study of Michel et al. provides no MRT images of the fetal heart.
The problem of interference between the CTG device and the MRT has been an unresolved problem for years.